It is well known that heart diseases may result in disorders of the cardiac valves. For example, diseases such as rheumatic fever can cause the shrinking or pulling apart of the valve orifice, while other diseases may result in endocarditis, an inflammation of the endocardium or lining membrane of the heart. The resulting defects in the valves hinder the normal functioning of the atrioventricular orifices and operation of the heart. More specifically, defects such as the narrowing of the valve stenoses and/or the defective closing of a valve, referred to as valvular insufficiency, result in an accumulation of blood in a heart cavity or regurgitation of blood past the valve. If uncorrected, prolonged valvular insufficiency may cause permanent damage to the leaflets, which may eventually necessitate total valve replacement.
These defects may be associated with any of the cardiac valves. For example, if the mitral valve stenosis connecting the left auricle and the left ventricle narrows, blood will accumulate in the left auricle. Similarly, in the case of mitral insufficiency, the mitral valve does not close perfectly, and blood in the left ventricle is regurgitated past the closed mitral valve into the left auricle when the ventricle contracts.
It is known to use annuloplasty rings in the repair of diseased or damaged atrioventricular valves that do not require replacement. The annuloplasty ring provides support for the mitral or tricuspid annulus and restricts expansion of the annulus or portions of the annulus to preset limits. A variety of annuloplasty rings have been employed, ranging from rigid rings of fixed size to flexible rings with a degree of adjustability. Obviously, annular prostheses that are of fixed size must be carefully selected and skillfully sutured in place. Even then, the functional result can be verified only at the end of the operation. Thus, an imperfect fit may greatly increase the duration of an operation or require corrective surgery to replace the improperly sized prosthesis.
U.S. Pat. No. 4,042,979 discloses an adjustable annular valvuloplasty ring which is said to overcome some of the problems associated with non-adjustable prostheses. The embodiment disclosed includes a frame that is sized and shaped to extend about a significant portion of the circumference of the orifice, an expandable member extending from the ends of the frame, and means for expanding and contracting the expandable member whereby segments of the ring and, accordingly, the segment shape of the orifice may be adjusted after implantation. U.S. Pat. No. 4,290,151 also discloses an adjustable annular prosthesis comprising a tubular body having a single flexible filiform string that is undulated with retention points that differentiate zones of contraction during use of the ring. This arrangement also permits some selective adjustment of the sector of the prosthesis between the retention points and the exit points of the string. The known annuloplasty rings, however, do not provide certain characteristics that are desirable to achieve successful implantation and correction of the disorder.